In order to get as much as possible shape-stable wood material with a hard surface and a pleasing appearance out of a log of wood, a so-called star-sawing technique is used in certain cases which gives, amongst others, triangular staves of wood. One such technique is described, for example, in the Swedish patent application No. 9100830-0. These triangular staves of wood can then be laid beside each other with their bases alternately turned upwards and downwards and joined together to form a large block. This block can be used as it is for table tops, floor material or the like but it can also be sawn up into thinner and/or narrower boards along or across the direction of the grain.
During manufacturing of glued blocks where the material consists of triangular starsawn wooden elements there sometimes occur large problems in getting the block perfectly glued when conventional techniques are used. The problems consist, amongst others, in that the friction forces on the upper and lower surfaces are much greater in the case where the force is applied in the conventional manner against the longside edges, i.e. against the outermost staves of wood in a laid-out series of staves of wood. The pressure from the press is lost the closer one gets to the middle of the block, which means that the glued joints near the middle become less durable.
WO 83/03791 describes a method and arrangement for making glue joint blocks according to the priorly known technics (see especially pages 11 and 12). The triangular staves of wood are provided on place between the lateral pressure plates which then are place having a distance between them adapted to the pattern of triangular staves which are layed on a lower board. In order to keep the staves on place during the pressure procedure the staves having their bases upwards are pressed down a little such that their tops are protruding downwards between the bases or the staves having their bases downwards and then fixed in that position. After that the pressure proceeding begins by pressing the lateral pressure plates together. Thus the pressure is here provided against the outer staves in the block.